Friday, September 14, 201210:00 amSet theory seminarGC 6417

The least weakly compact cardinal can be unfoldable, weakly measurable and nearly theta-supercompact

Joel David Hamkins

The City University of New York

Joel David Hamkins

Starting from suitable large cardinal hypothesis, I will explain how to force the least weakly compact cardinal to be unfoldable, weakly measurable and, indeed, nearly θ-supercompact. These results, proved in joint work with Jason Schanker, Moti Gitik and Brent Cody, exhibit an identity-crises phenomenon for weak compactness, similar to the phenomenon identified by Magidor for the case of strongly compact cardinals.

Professor Hamkins (Ph.D. 1994 UC Berkeley) conducts research in mathematical and philosophical logic, particularly set theory, with a focus on the mathematics and philosophy of the infinite.  He has been particularly interested in the interaction of forcing and large cardinals, two central themes of contemporary set-theoretic research.  He has worked in the theory of infinitary computability, introducing (with A. Lewis and J. Kidder) the theory of infinite time Turing machines, as well as in the theory of infinitary utilitarianism and, more recently, infinite chess.  His work on the automorphism tower problem lies at the intersection of group theory and set theory.  Recently, he has been preoccupied with various mathematical and philosophical issues surrounding the set-theoretic multiverse, engaging with the emerging debate on pluralism in the philosophy of set theory, as well as the mathematical questions to which they lead, such as in his work on the modal logic of forcing and set-theoretic geology.